Rear suspensions for bicycles are known. However, most of these have not proven entirely satisfactory in practice.
In most prior art rear suspension assemblies, the rear axle pivots about a single point when subjected to the bump force, as when traversing rough terrain. This results in the pedaling forces tending to either compress or extend the spring/damper assembly of the rear suspension. In this respect, then the spring/damper assembly of the rear suspension is affected by the pedal force, some of the rider's energy is needlessly wasted to compress the spring/damper assembly. This effect is illustrated by the common tendency of most prior art rear suspension systems to either lock up or "squat" when the rider pedals. Since these prior art rear suspension systems are generally designed having a single lever arm which pivots about a single quadrant, the lock up or squat generally occurs as a result of chain tension acting on the single lever arm. If the single pivot line of the rear suspension system is above the chain line, the suspension will typically lock up and/or "jack", thereby providing suspension only when the shock or pump force exceeds the chain tension. Conversely, if the single pivot point of the rear suspension system is below the chain line, the system will typically squat since the chain tension is acting to compress the spring/damper assembly of the rear suspension system in the same manner as does the shock or bump force.